Virgo Logbook

Since this morning, SNEB controls are noisy. The operator called me to see how to improve this. I noticed that the SNEB_LC process was resynchronized around 9am and that the TY-large error flag was on, so the bench cannot be damped in low-noise mode. I tried to reduce the bench coil correction by changing the setpoint of F1 a little bit, although I think it was already centered, and later by rotating the wire with stepper motor 5. However, the horizontal coils providing the TY correction all are below 0.5 V (I lowered it from ~0.8 V to ~0.3 volts by rotating Ty a bit). 2 vertical coils, FR_V and BL_V, are around + and - 4 V however, with FL-v and BR_V at + and - 2 V. Thus there is a positive Tz and Tx offset that is too large; the 4 V do not allow the low-noise mode of the bench I think.
In order to remedy that, I recommend that the LAPP group has a look at the SNEB_LC settings, I expect that a small movement of the counter masses is necessary to balance the bench and bring the vertical correction closer to 0.